Electric signaling



April 16, 1929.

E. T. BURTON ELECTRIC SIGNALING Filed Nov. 6, 1926 2 Sheets-Sheet lApril 1'6, 1929. E. T. BUR'roN ELECTRIC SIGNALING Filed Nov. 6, 1926 2Sheecs--SheeI 2 #Wen/aft' A fm .Patented Apr.' 16, 1929.

' UNITED STATES 'PATENT o Prior-:.4

EvEnETT T. BURTON, or JAcxsoN HEIGHTS, NEW roms, AssioNon To :BELLTELE'. rHoNE LABORATORIES, INCORPORATED, OE NEW yoiix, N. Y., ACORPORATION F NEW YORK.

ELECTRIC SIGNALING.

The invention relates toelectric signaling and particularly to carriercurrent telegra h iAnyobject of the invention is to simplify theoperation and 'maintenance of carrier current telegraph systems. i

Another object of the invention is to reduce distortion in telegraphsignals at terminal and repeater points.

The invention provides, a simple and 'etlicient telegraph system inwhich a single carrier frequency is employed for alternate transmissionin two directions over each coinniunication channel. In transmittingsigi5 nals, the carrier current is impressed upon the line during aspacing interval and is cut of during a marking interval.A A vacuum,

tube receiving circuit or an alternating current receiving relay in eachchannel responds directly to the incoming and outgoing carrier currents.

Heretofore, in transmitting telegraph .signals it has been customary tocontrol the receiving relay at the transmitting terminal a5 from thelocal direct currentfcircuit rather than from the carrier transmissioncircuit, and in receiving signals to rectify the in coming carriercurrents to operate the receiving relay. By operating the receivingrelay directly in response to incoming and outgoing carrier currentsthe' invention effects a material saving in signaling apparatus.Furthermore, operation of the near 'end sounder from the outgoingcarrier allows dll ing signals lag on the make by the time of travel ofthe direct current relays and lag on the break by the time of travelofthe alternating current relays.` According to the invention, the timelag` between make and the sending .operator to monitor directly on breaksignals is made uniform, thus eliminating distortion in the signals suchas is commonly caused by the time ofarmature travel in the operation ofrepeater relays.-

The invention will be described` in connection with the accompanyingdrawings in which` similar reference characters designate similar partsin the several figures, and 1n which:

Fig. 1 is a diagrammatic illustration of a carrier current telegraphsystem including terminal and repeater circuits embodyinr the invention;.is

Fig. 2 is a diagrammatic illustration of a termlnal circuit which may beused in place of the terminal circuit shown in Fig. 1; and U Fig. 3 is adiagrammatic illustration showing modified terminal and Reference willrst be made to the multipleX carrier current telegraph' system shown inFig. 1 which includes the west terminal a mid-line repeater interconnected by the transmission line section L1.

The usual east terminal, which is identical to the west terminal shownin Fig. 1, is omitted for the ysake of\ simplifying the showing, but inApractice may be connected to the repeater by means of line section L2.u The terminal and repeaterl circuits may include a plurality of two-waycommunication channels ince these channels are identical except as tothe frequencies which they employ, only detail and additional channelsare merely indicated by the leads connected in parallel `with the linesection L1 at the terminal and repeater.

Carrier currents of different frequencies are transmitted over theseveral channels of thesystem. Each channel requires but one carrierfrequency for complete two-way communication, and hence fewer selectivecircuits are needed to separate the different channel frequencies thanare needed in systems employing dii'erent frequencies in each direction.

The carrier telegraph channel which is illustratedin detail at the westterminal includes a band filter BF,L which passes currents of thefrequency assigned to this channel and. suppresses currents of otherfreone channel is shown inrepeater circuits.

' cuited at the closed contacts of an auxiliary v yEF1, to the lowerline conductor.

quencies. Similar band filters BF,- and BFI are associated with thischannel at the repeater. The filters employed throughout the system maybe of the ty e disclosed 1n U. S. Patent No. 1,227,113 to A. Campbell,issued May 22, 1917.

The apparatus at the west terminal 1n-v cludes a carrier frequencygenerator 5 which is connected to the band filter BF1 through thewinding of an alternating current relay 6 which matchesthe impedance ofthe band filter. When no signals are being' transmitted, the carrieroscillator is short-cirswitch 7. through a resistance network 8.

vWhen no signals are being transmitted or received the relay 6 isdeenergized, or in the markingosition shown in the drawing. In thiscondition the sounder 9' is energized over a circuit extending fromgrounded bat- :tery 10, through the winding of sounder 9,

contact and armature of relay 6 to ground. Incoming carrier currentspass through the upper conductor of line section L1, filter EF1, windingof relay 6,` switch 7 filter The current in this circuit causes therelay 6 to attract its armature, opening the circuit of sounder '9. Whenthe switch 7. is opened and key 7 open, the outgoing currents from thegenerator 5 flow through relay 6 to line section L1, also causing theoperation of the sounder 9. The sounder is thus operated in accordancewith incoming and outgoing spacing and marking signals.

In case either terminal key is open, that is, when the oscillators atthe respective terminals are not short circuited, carrier current flowsthrough relay 6. If, therefore, the receiving operator at the eastterminal wishes to break in-on the transmission from the west terminal,he opens his key and the transmittin sounder 9 fails to follow theoperation o transmitting key 7 because relay 6 will be continuallyactuated.

The repeater includes an alternating current relay 11 associated withline section L1 and a similar relay 11 associated with line section L2.When no carrier currents are incoming at the repeater from either 'linesection the circuits are as shown in the drawing. In this condition arelay 12, controlled by the relay 11, is energized over a circuitextending from grounded-battery 13, through winding of relay 12 toground, and a similar relay 12 assoclated with the relay 11 is energizedover a similar circuit. local carrier generator-14 is connected incircuit with resistance network 15 when no signals are received at therepeater, and is arranged to' be connected tol either line sectionwhenever carrier current is received from the opposite line section.

the upper line conductor, filter BF lefthand winding of relay 11,armature and front contact of relay 12', filter BF, to the lower lineconductor. The relay 11 thereupon operates, and upon opening its contactreleases the armature of relay 12 by breaking the vlocal battery circuitpreviously traced. The relay 12 1n deenergizing closes its back contact,connecting the local oscillator 14'to the line section L2, so thatcarrier current flows over a circuit extending from the upper conductorof line section Ll through filter BF ri ht hand winding of relay 11',armature of ack contact of relay 12, left hand winding of relay 11',resistance network 15, oscillator 14, filter BF to the lower lineconductor. In this condition the windings of relay 11 are connected inseries opposin relation and hence this relay is not operate by thecarrier current from the oscillator 14. When the carrier current on lineL1 is cut-off at the end of a spacing signal, the relay 11 is deenerized and its armature returned to the mar ing position shown in thedrawing, thus com leting the energizing circuit of relay 12 whichdisconnects the oscillator 14 from line section L2. It will be seen thatthe repeated spacing signals lag on the make by the time of travel ofthe armature of relay 12 since the carrier source 14 is not connected toline section L2 until the armature of relay 12 reaches its back contact.It will also be seen that the spacing signals lag on the break by thetime of travel of the armature of relay 11, since the source 14 isdisconnected from line section L2 when the armature of this relayreaches its contact. These relays are so constructed that the times oftravel of -their armatures are identical and hence there is no bias in4the repeated signals. The repeater is symmetrical in respect to the linesections L1 and L2, signals transmitted from east to west being repeatedin the same manner as the signals transmitted from west to east.

Fig. 2 shows a modified terminal circuit arranged for connection to asubscribers loop. This circuit includes an alternating currentreceiving` relay 16 having two windings, and arranged to respond equallyto the transmitted and received carrier currents. Only the right handwinding of this relay is connected to the line section L1 when signalsare being received, and both windings are connected in series opposing'relation with the line section when spacing signals are beingtransmitted. The left hand winding of relay 16 is tapped at anintermediate point so that the differential ma etizing force produced bythe transmitte carrier current in both windings is approximately equalto that produced by the weaker received current in the right handwinding. Hence this circuit arrangement eliminates inequality in theoperation of the rela which would otherwise result from the di ferencein value of the transmitted and received currents.

A direct current relay 17, also having two windings, is arranged toconnect the carrier generator 5 to the line section L1, during a spacininterval and to disconnectt-he oscillator rom the line section during amarking interval. Then the circuit is in the condition shown in thedrawing the left hand winding of rela-y 17 is connected to thesubscribers loop over a circuit extending from the negative side ofgrounded battery 18, through a battery series resistance 18', closedcontacts ot switch 7a, winding of sounder 9, high resistance 19, lefthand winding or .re-v lay 17, battery resistance 20to 'the posltive sideoit grounded battery 20.` The current Howing in this circuit issufficient to operate the relay 17 but is insuilicientto operate thesounder 9. Y However, under such condition the right hand winding ofrelay 17 l1s connected to the subscriber s loo over alow re-v sistancecircuit extending rom tlfrefnegai-` tive side et grounded battery 18,throughv resistance 18, closed contactsof switchv winding ot sounder 9,contact'and armature ot relay 16, right and lett hand windings oi lrelay 17resistance-20 to the positive vside otgrounded battery 20.Thiscircuit carries an increased current suilicient to operate' thesounder 9. rlhe windings of relay 17 are wound in opposition and are sorelated in the number of turns that the eil'ect of the additionalcurrent fiowing through the subscribers loop during a markinginterval,-wlliczh` is the condition shown in the drawing, is

substantiall neutralized in therelay 17 ,thus protecting t e core ofthis relayfrom exces-r sive magnetizing forces. '1 j e lncoming carriercurrents which are passed by the band filter BF, pass through the righthand winding of alternating cur-v rent relay 16, causing this Lrelaytojiattract its armature and open the low resistancerem` ergizingcircuit of the sounder 9. The currv rent which still flows fromgroundedbattery l,18, through resistance 18 switch 7a, sounder 9resistance 19, left han winding of relay;

ergized but, as previously noted, is insuiiicient to operate the sounder9. The sounder interval when carrier currents are received 9 istherefore deenergized during the spacing from the line section L1. `Atthe termination v of a spacing signal the relay 16 is deenergized,closing its contact and again establish-'- around the resistance 19.

ing the energizing circuit Afor thesounder9 In Order to transmitSignals, the transmit;

i ting key 7 is closed and the switch 7a opened.

sounder 9 and relay 17. The relay 17 in releasing its armature connectsthe generator 5 to the line section L1, permitting carrier current toflow over a circuit extendmg from the lower line conductor, throughfilter BF1 generator 5, resistance network 8, left hand winding of relay16, back contact and armature of relay 17, right hand winding of relay16, filter BF1, to the upper line conductor. rlhe current liow'ing inthis circuit causes` the relay 16 to attract its armature. Wheri thetransmitting key 7 ispagain closed, the relay 17 is energized over acircuit similar tothat previously traced .through the left hand windinerot this relay and resistance 19, but inclut ing the contacts of key 7instead-ofl switch 7,L which is now open. The current in this circuit,however, is insufcient to attract the armature of the sounder 9. Therelayl 17 'in attracting its armature opens its back Contact, thusdisconnecting the generator 5 from the line section L and deenergizesthe relay 16, to complete the low resistance energizing circuit ofthe'sounder 9. The front contact of relay 17 is also closed,conditioning the circuit to transmit or receive further s1 nais. When nosignals are to be transmitte switch 7a is closed.

This circuit also allows the receiving op erator to break in on thetransmission by opening his local circuit and sending carrier over theline. If the east terminal operator breaks in, the sounder 9 will notfollow the operation' of the west terminal key 7 since relay 16 remainsactuated, preventing suiiicient current from reaching the sounder tooperate it. vRelay 16 remains actuated because'current will be suppliedto it either from the receiving station through the right hand windingof the relay or from the geni erator 5 through both windings of therelay.

In the modification of the invention shown in Fig. 3 space dischargetube detectors are employe in place of the alternatlngcurrent relays atterminal and repeater points. The operation of the system in receivingsignals at the west terminal will first be described. Incoming carriercurrents lpassed bythe band filter BF1, pass through the upper lineconductor of line section L1, 17, andresistance 20 to groundedvbattery-20, is suilicient to maintainv the relay*` 17 en-i* v,cuit induces avoltage in the right hand winding of transformer 21 connected in theinputl circuit of a three-element space,` discharge tubedetector 22.Space current is thus caused to How in the output circuit of this tubefrom grounded battery 25, through the right hand winding of relay 24,priing the sounder to release its armature. As

ary winding o f transformer 23 is connected lto an auxiliary windin` ofrelay 24, and a change of current in t is circuit causes a building upof flux which accelerates the opera-tion of the relay, as is commonpractice in telegraphy.. he relay 24 attracts its armature, opening thelow. resistance energizing circuit ofthe sounder 9 and caus- *in thecircuit of Fig. 2, the current flowing from grounded batter 20, throughthe right hand winding of re ay 17, resistance 19, 'winding of sounder9, closedcontacts of switch the sounder. When the incoming carriercurrents are cut off s ace current ceases to flow in the output circuitof the detector tube 22 and the relay 24 is deenergized, re-

establishing the energizing circuit of they sounder 9. l

In transmitting signalsfrom the west terv minal, the key 7 is closed andthe switch 7. is o ened. y The key 7 is then opened, thereby eenergizingthe sounder 9 and relay17. The .front contact of relay 17 is thereforeopened and the back contact is closed, connecting the carrier generator5 to the line section L1. Thev outgoing carrier current flows over acircuit extending from the lower line conductor, through filter BFI,generator 5, resistance network 8, left hand winding of transformer 21,back contact yand `armature of relay 17, central winding of transformer21, filter BFI, tothe upper line conductor. The central and left handwindings of transformer 21 are connected in opposition and the backcontact of rela 17 1s connected to an intermediate tap o the left handwinding of the transformer so that the magnetizing forcesl produced bythe L transmitted and received currents in this transformer areapproximately equal. The outgoing current produces an induced voltage inthe right hand winding of transformerl 21 which causes space current toflow through the relay 24 in the output circuit of the detector tube 22,causing the relay 24 to attract its armature and open the energizingcircuit of the sounder 9, which is also broken at the open contact oftransmitting key 7. When the key-7 is again closed -the relay 17 isenergized over a circuit similar to that .previously traced through theright hand winding of this relay and the winding of sounder 9, butincluding the contacts of key 7 instead of switch 7 a which is now open,current flowing in this circuit, however, is insufficient to operate thesounder. The relay 17 thereupon attracts its armature, disconnecting thegenerator 5 from the line section L1. Since space current ceases to flowin the output circuity of the detector tube 22, the relay 24 isdeenergized, completing the low resistance energizing circuit of thesounder 9throu h both windings of relay 17. Also,

7, toground, is insufiicient to operate\\upper winding of thistransformer which causes space current to flow in the output circuit ofdetector tube'28 which includes the winding of relay 27. The relay 27thereupon attracts its armature, opening its back contact and closingits front contact, thereby impressing carrier current from the generator14 upon line section L2 over a circuit extending from the upper lineconductor, through filter BFS, central winding of transformer 26",armature and front contact of relay 27', lower winding of transformer26', resistance network 15, generator 14, filter BF3 to the lower lineconductor. In this condition the central and lower windings oftransformer 26 are connected in series opposing relation and hence thereis no increase in potential across the input circuit of the detectortube 28 and no current Aflows through ,the relay 27 in the outputcircuit of this tube. When the carrier currentl on line L,l is cut offat the end of a spacing signal the relay -27 is decnergized and itsarmature returned to the marking position shown in the drawing,disconnecting the generator 14 from the line section In order to preventcapacity coupling of the carrier current to the transmission linesections, the windings of relay 16 of Fig. 2 and the windings of balancetransformers 21, 26, and 26 of Fig. 3 may be separated by suitableshielding devices.

Although the invention has been described in connection with certainspecific embodiments, it is also susceptible of numerous othermodifications without departing from the scope and spirit of theinvention as defined by the appended claims.

What is claimed is:

1. A carrier current telegraph system comprising a transmission lineover which signals are transmitted in both directions, a terminalincluding a receiving relay and a source of carrier current connected inseries with said line, and means for rendering said relay responsiveonly to incoming signals, said means including means for shortcircuiting said source.

2. A carrier current telegraph system comprising a transmission lineover which signals are transmitted in .both directions, a

lll.)

terminal including a receiving relay and a source of carrier currentconnected in series with said line, and a 'transmitting key adapted todirectly short circuit said source when no signals are transmitted fromlsaid terminal and to remove said short circuit to Arender said relayresponsive to incoming signals.

v3. A carrier current telegraph system comprising a transmission line, aterminal including an alternating current relay in series with said lineand responsive te incoming signals, a transmitter including a source oitsustained carrier current at said terminal, and means for connectingsaid source in series with said line and relay to actuate said relay inresponse to outgoing signals.

4.* A carrier current telegraph system comprising a transmission linehaving two conductors, a terminal including an alternating current relayin series with said conductors and responsive to incoming signals, atransmitter including a source of carrier current at said terminal, andmeans including a transmitting key for directly connecting said sourcein series with said conductors to actuate said relay in response tooutgoing signals.. v

5. A carrier current telegraph system 'comprising a transmission lineover which carrier currents are transmitted in both directions, analternating current relay having a winding in series with said line andresponsive to current transmitted in one direction, a source of carriercurrent for transmission in the opposite direction, means for.connecting said source to said line through said relay winding, andmeans for making the total magnetizing force of said relay produced bythe current transmitted in one direction equal to the magnetizing forceof said relay produced by the currents transniitted in the oppositedirection.

G. A carrier' current telegraph system comprising a transmission lineover which carrier currents are transmitted in both directions, and analternating current relay having a winding in series with said line andresponsive to current transmitted in one direction and a second 'windingadapted to be connected in opposition to said first mentioned winding inresponse to current transmitted in the opposite direction, said wind--ings being proportioned to maintain the magnetizing force produced bythe current in both windings approximately equal to that produced by thecurrent in said first mentioned Winding.

7. A carrier current ltelegraph system comprising a transmission lineover which carrier currents are transmitted in both directions,a circuitassociated with said line and including a receiver responsive toincomand outgoing currents, and a plurality of electrical windings insaid circuit prol ings.

portioned to maintain the operating forces exerted upon i said receiverby current in both directions approximately equal.

8. carrier current telegraph system comprising a transmission line overwhich carrier currents are transmitted in both directions, a terminalincluding an alternating current relay having a winding in series withsaid line causing said relay to be responsive-to incoming currents, anda second winding adapted to be connected in oppo sition. to said firstmentioned winding both of said windings causing said relay to beresponsive to outgoing currents, said windings being proportioned tomaintain the magnetizing forces produced by the incornn .A ing andoutgoing currents therein approximately equal.

9. carrier current 'telegraph system comprising a transmission line overwhich carriercurrents are transmitted in both directions, a terminalcircuit including a source of carrier current, a relay adapted whendeenergized to connect said source to said line, a receiver connected inseries with said relay, and means responsive to incoming carriercurrents to actuate said receiver without deenergizing said relay.

10. A vcariier current telegraph system comprising a transmission lineover which signals are transmitted in both directions, a terminalcircuit including a carrier current generator, a relay having twowindings adapted when deenergized to connect said enerator to said line,an energizing circuit or one winding of said relay includinga receiverand a source of current suilicient to operate said relay butinsuificient to operate said receiver, an energizing circuit for saidreceiver including 'said source and both,

windings of said relay, and means responsive to incoming signals to openand close said second mentioned energizing circuit.

l1. A carrier current telegraph vsystem comprising a transmission lineover which signals are transmitted in both directions, a terminal-circuit including a carrier current generator, a relay having twowindings adapted when deenergized to connect said generator to saidline, an energizing circuit including a receiver in series with onewinding of said relay and a source of current sufficient to operate saidrelay but insuiiicient to operate said receiver, and an energizingcircuit for said receiver including said source and both"windings ofsaid relay, the windings ofsaid relay being proportioned to maintain themagnetizing force produced by the current in said iirst mentionedwinding approximately equal to the magnetizing force produced by thecurrent 1n both wind- 12. comprising two line sections over whichcarrier currents are transmitted in both di- A carrier current telegraphsystem.

rections, a device having an armature re. sponsive to carrier currentstransmitted' over one line section, a relay adapted to deenergized uponthe energization of said device, a source of carrier current, means toconnect said source to the second line sec" tion upon the deenergizationof said. relay7 and to disconnect said source from said sel ond linesection upon the deenergizatlonof said relay, and means including saidfirst means and said armature of saidD device for making theintervalbetween signals over said second line section of the sameduration as the interval between signals over said y tions, analternating current rela v irst line section. s f

13. A carrier current telegraph s stem comprising two line sections overwhic carrier currents are transmitted in both direcresponsive to carriercurrents transmitte over one line section, a direct current relayadapted to be deenergized upon the energization of tions, an alternatingcurrent relay having an armature operative in response to carriercurrents transmitted over one line section, a direct current relayadapted to be deenergized to release its armature upon the energizationof said alternating current relay, and a source of carrier currentadapted to be connected to the second line section upon thedeenergization of said direct current relay and adapted to bedisconnected from said second line section upon the deener ization ofsaid alternating current relay, sai relays bein so proportioned that thetimes of travel o their armatures are substantially equal.

15. A carrier current, telegraph system comprising a transmission lineover which signals are transmitted in both directions, termmal circuitseach including a carrier current generator, a recorder of signalsreceived and transmitted over said line, an alternatin currentrelayoperating said recorder, said incoming and outgoing signalsactuating said alternating current relay, and means at each terminallfor disabling the operation of said alternating current relay and saidrecorder at the opposite terminal when signals are being transmittedfrom the opposite terminal.

In witnessAwhereof, I hereunto subscribe my name this 29th day ofOctober A. D.,

EVERETT T. BURTON.

